Combustion apparatus



Feb. 8, 1944. f E. A. BOVEE 2,341,355

comsusuou armmus l Filed uamn'rr. 1941 2 Sheefis-Sheet 1 INVENTOR. 54/40 ,6. 501/55 Patented Feb. 8, 1944 COMBUSTION APPARATUS Eliad A. Bovee, Lansing, Mich., assignor to M- tor Wheel Corporation, Lansing, Mich, a corporation of Michigan Application March 17, 194l, Serial No. 383,773

1 Claim. (Cl.'158 91) This invention relates to combustion apparatus of the type employing vaporizing pot type burners. More particularly, the invention relates to the heat chamber shells and burners therefor.

It has been recognized for some time that all of the air, both primary and secondary, utilized for combustion in combustion apparatus of the above mentioned type, should be metered. Furthermore, for the best performance of the apparatus, the secondary air should be properly distributed within the combustion chamber. 3

Heretofore, in certain prior art devices of this type, part of the secondary air has been admitted through air inlet openings provided for the purpose in the burner side wall, and the remainder has leaked between the burner side wall and the heat chamber side wall. It has only recently been recognized that the air that leaks between the two walls is not metered, and is not uniform in different heaters of the same size and style. The leakage is due not only to differences in diameter of the parts, but to differences in shape. Irregularities in the contacting surfaces have always been present.

The principal object of this invention is to provide a form of construction for the heat chamber and a form of construction for the burner whereby to obtain a uniform substantially airtight joint between them and at the same time facilitate the installation of the burner within the heat chamber. This object is attained by forming the burner to provide adjacent the upper end an annular exterior surface of exact predetermined circumference for engagement with the heat chamber shell, and forming the heat chamber shell to provide a plurality of annular sections having internal circumferences decreasing in order from the bottom of the shell upward, one of the smaller sections having substantially the same internal circumference as the circumference of said exterior surface of theburner and having its lower end spaced from the lower end of the shell a distance at least as great asthe distance between the bottom of the burner and the said exterior surface thereon. Thus, the burner may be conveniently inserted into the lower end of the shell and. the said exterior surface of the burner brought into substantially airtight engagement with said smaller section of the shell without the necessity of forcing the burner all the way from the lower end of the shell to its final position therein.

The aforementioned object will become more apparent in the following specification when read in connection with the accompanying drawe ings, wherein 1 Figure 1 is a vertical cross-sectional view of a heater embodying the invention;

Figure 2 is a cross-sectional view of an expanding die employed for sizing the heat chamber shell, and the heat chamber shell in place there--v on;

Figure 3 is a cross-sectional view of the completed side wall of the heat chamber shell; and

Figure 4: is a cross-sectional view of an expanding die for sizing the burner, and the burner side wall in place thereon.

Figure l discloses a heater of the so-called radiant type embodying a heat chamber I0 and a vaporizing pot type burner I2. The heat chamber comprises a tubular heat chamber shell II, atop wall I3 in sealed engagement therewith, and a bottom .wall I4 in telescoping relationship with the lower end of the shell. The heat chamber has a door opening I5 to permit access to the interior thereof. It is provided. also with a flue outlet I6 adjacent the upper end thereof.

The heat chamber shell I I is formed from sheet metal and is of elongated tubular shape. The heat chamber shell shown is divided into five sections I'I,,I8, I9, 20 and 2|, of varying internal circumferences. The three uppermost sections I1, 2!] and 2| form the combustion chamber. Below the combustion chamber is an accurately sized narrow annular section I9 having a predetermined inner circumference greater than that of the combustion chamber section II. Below the section I9 is an air jacket section I8 having an inner circumference greater than that of section I9.- The height of section I8 is approximately the same as the depth of the burner I2. Preferably the upper end of the heat chamber shell is formed exactly the same as the lower end. The u per end section 20 of the combustion chamber section has the same diameter as that of the air jacket section I8. Just below the section 20 is a narrow annular section 2I', the diameter of which is the same as that of the section I9.

The burner disclosed herein comprises a tubular sheet metal side wall 22 and a bottom wall 23 secured to the lower edge of the side wallin sealed engagement therewith. Adjacent the upper edge of the burner side wall is an accurately sized outwardly extending bead 24. An inwardly extending bead 25 supports a top wall 26. An anti-explosion baflie 21 is seated upon the top wall 26. Within the burner is a cen trally apertured partition 28.

. The side wall 22 of the burner has a plurality of rows of primary air inlet openings 29, and just above the top wall 26 it is provided with two rows of secondary air inlet openings 30 and 3|. The air inlet openings are properly sized and distributed throughout the burner side wall so as to accurately meter the air and distribute it within the burner and combustion chamber.

The annular section I9 of the heat chamber shell and the bead 24 on the burner side wall are sized so that the respective circumferences of their adjoining surfaces are substantially the same. The inner circumference of the section I9 is preferably exactly the same as that of the exterior surface of the bead, but it may be slightly larger due to manufacturing tolerances. The variation is not over inch in circumference or .005 inch in diameter. The fit between the section I9 and the bead 24 is such that it requires considerable pressure to force the burner into the annular section I9, but is not so tight that it prevents removal of the burner from the heat chamber shell if desired. The joint thus produced is substantially air-tight. It is estimated that not over 3% or 4% of the total air admitted to the burner can leak between the bead 24 and the section I9. What little leakage there is will always be uniform.

The air jacket section I8 of the heat chamber shell is made slightly larger than the intermediate section I9 to facilitate the assembly of the burner and heat chamber shell. The enlarged section I9 acts as a pilot for the burner I2, yet permits the burner to be inserted without applying any pressure until the burner enters the intermediate section I9. The distance through which the burner is moved after pressure is applied is very short. This feature is an essential part of the invention. If the sections I8 and I9 were of the same size it would be practically impossible to assemble the burner and heat chamber without stretching one or compressing the other unless the heat chamber side wall were made considerably larger than the burner head 24. That would defeat the purpose of the invention because it would permit considerable leakage of It is possible to fit the bead 24 into the section I9 so tightly that there will be no leakage what-- ever. Such a tight fit, however, would not only make it more difficult to assemble the burner and shell, but would practically prevent removal of the burner in case it is desired to clean or repair it after it has been placed in service. Therefore, it is not desirable to fit these two parts too tightly together.

In a preferred method of making the invention the heat chamber shell is fashioned by coiling a flat sheet of metal into tubular form, and thereafter welding the adjacent edges of the sheet together. The shell is then placed upon the die shown in Figure 2, and the enlarged sections I8 and IS'a-re formed by the die.

The die shown is a conventional expanding die. It is composed of a plurality of radial sections 35 mounted on a'base 35 for sliding movement in a radial direction. Betweenthe sides of the base and the sectiens 35 are a plurality of coil springs 31"which urge the sections 35 toward the center o'f'the die. 'In the center of the die is a frust'oconical Wedge 38 attached to a shaft 99 extending through a hole in the base. A downward pull on the shaft 39 will cause the wedge 93 to spread the sections 35 radially outwardly. The sections 35 are moved only a predetermined distance. That distance is determined by amount of movement of the wedge 38. The sizes of the sections I8 and I9 are controlled by the amount of movement of the wedge 38.

The tubular heat chamber shell is placed upon the die as shown in Figure 2, and the sections 35 are spread by exerting a downward force on the shaft 39. This stretches the metal of the shell into the shape shown in Figures 2 and .3. The two sections l8 and I9 are thus accurately sized.

The upper end of the heat chamber shell may be left in its original form, but preferably it is sized in the same manner as the lower end of the shell. It is easier to provide a tight joint between the top Wall I3 and the side wall II of the heat chamber shell if the upper end of the heat chamber shell is sized, and by sizing the upper end the same as the lower end requires but one die for both operations.

The side wall 22 of the burner I2 is formed from sheet metal coiled into tubular form, as shown in Figure 4. After coiling the side wall it is rolled in a conventional rolling machine to form the bead 24. The burner side wall is then placed upon the die shown in Figure 4, which is of the same general construction as the die shown in Figure 2, but of a different outside configuration. The burner side wall is expanded in this die so that the outside diameter of the head 24 will fit snugly within the section I9 as above described.

After the side wall 22 of the burner is sized it is attached to the bottom wall 23, and the partition 28, the top wall 26 and the anti-explosion baffle 21 are secured within the burner. The burner assembly is then inserted into the heat chamber shell with the bead 24 in contact with the section I9, as described previously. The bottom wall I4 of the heat chamber shell is then secured. to the burner to hold the same in its proper position.

The method of sizing the side wall of the heat chamber shell and the bead 24 on the burner produces very accurate results. It is possible to size the parts to within plus or minus %4 inch of the desired circumference, or in other words, within less than plus or minus .005 inch in diameter. In sheet metal work such tolerances are exceedingly close. The chief reason for tolerances of the order mentioned lies in the variations in thickness of the sheet metal employed.

It will be evident from the foregoing descrip.'- tion that this invention eliminates manyof the difficulties inherent in previous heaters of this type. The invention provides a structure in which it is a relatively simple matter to provide the desired tight joint between the burner and the heat chamber shell. lhe tight fit substantially eliminates leakage and permits the burner to be provided with the proper number of sec ondary air inlet openings to accurately meter the secondary air. The invention also provides a structure which can be manufactured and'as sembled with a minimum of difficulty, because the burner is readily inserted into the air jacket and is pressed for but a short distance into the intermediate section I9.

The scope or the invention is indicated in the appended claim.

I claim: T

Combustion apparatus comprising a pot type burner having an outwardly extending annular bead adjacent its upper end sized to a predeter mined circumference, and a heat chamber shell surrounding the burner, said heat chamber shell comprising a plurality of annular sections having internal circumferences decreasing in order from the lower end of the shell upwardly, a section above the lowermost section being substantially cylindrical and being accurately sized to substantially the same internal circumference as the circumference of said bead, the section below said cylindrical section being of greater internal circumference than the external circumference of said bead, said cylindrical section of the heat chamber shell being of substantial axial extent and said bead on the burner engaging said cylindrical section in a zone intermediate axial extremities of the cylindrical section and substantially throughout the circumference thereof.

, ELIAD A. BOVEE. 

